What kind of race track? Humans, horses, dogs, and cars all vary in speed, which are all determining factors (photographing dogs is vastly different than shooting super fast cars). Do you want to show motion? Freeze action?

I was at the Gatornationals last weekend and took a ton of pictures of the top fuel dragsters going about 300mph. It took A LOT of trial and error to get it right, but that's why I made sure to get there in time for pre-races. Practice!

I found that I ended up needing a pretty high ISO even though it was sunny out. At ISO 200 I was only able to get up to about 1/1000, which showed a lot of motion. And in pre-races when the cars were significantly slower, I knew I'd have to up the anty for faster cars. Finally I settled on 800 (ISO) and was able to get my shutter speed to 1/3500 at times (when the sun didn't hide behind the clouds). Aperture wasn't all the way open, but close.

LOTS of film. If you're asking us for settings, you'll blow through a ton of it fairly quickly. My first time taking photos of motorcycles with a DSLR and doing panning shots got me a keep ratio of about 1 out of every 15 or so.